Monoamines in the C cells of the thyroid gland of callithricid primates.

The thyroid gland of three species of marmosets were studied with the Falck and Hillarp fluroescence technique for monoamines. Two types of fluorescent C cells were observed. The predominant type displayed the greenish (or blue) fluorescence characteristic of catecholamines. The other type displayed a yellowish fluorescence most probably due to 5-HT. The presence of monoamines in C cells now reported for the first time in Primates offers an interesting possibility for studying their presumed role in calcitonin secretion.